Community structure of gelatinous zooplankton in a temperate ecosystem: Spatial patterns and underlying drivers

Gelatinous zooplankton (GZ) have long been regarded as organisms taking over perturbed systems (e.g. competing with fisheries and damaging aquaculture), but more detailed studies are required in order to better understand their role in marine ecosystem functioning. The present study characterised the GZ in the Bay of Biscay (BoB), (1) determining biodiversity, abundance and community composition of GZ assemblages, and (2) exploring the influence of oceanographic variability on GZ communities. Simultaneous GZ and oceanographic samples were obtained in May 2011 from 100 hydrographic stations. From the 30,194 GZ specimens analysed, 19 taxa were identified within Appendicularia, Thaliacea, Hydrozoa, Scyphozoa, and Tentaculata classes. There were few highly abundant taxa (e.g. Fritillaria pellucida represented almost the 60% of the collected individuals), but most of the species were diverse and less common. The most common species showed heterogeneous spatial abundance patterns, structuring 6 assemblages. Spatial configuration of GZ was shaped by depth, mean salinity and total chlorophyll a, suggesting a close relationship with main mesoscale oceanographic features in the BoB, such as shelf-break fronts and river plumes. This novel information complements the limited existing information of the main abundant gelatinous species within the “Bay of Biscay and Iberian coast ecoregion” of the Marine Strategy Framework Directive and could provide useful data for future ecosystem-based monitoring efforts.